Nice crunch! Click the arrow to hear the sound of Philae touching down on Comet 67P/C-G on November 12, 2014. To hear the file as many times as you’d like, click the SoundCloud icon that appears after the first play.
Listen. Hear it? Mixed with the sound of flexing landing pads when Philae first touched down on the comet’s surface is – what sounds to my ear – like the crunch of comet grit. Sensors in the feet of the lander recorded the moment of contact during Philae’s first attempt at landing on November 12th.
It was recorded by the instrument SESAME-CASSE, which was turned on during the descent and clearly registered the first touchdown in the form of vibrations detected in the soles of the lander’s feet. We’re listening to a real sound file - a recording of mechanical vibrations at acoustic frequencies – not a simulation. No changes in frequency were made, so it sounds just the way it would if you could have stuck your head inside Philae with your ear in contact with the landing gear when it made contact with the surface.
Klaus Seidensticker from the DLR Institute of Planetary Research says: “Our data record the first touchdown and show that Philae’s feet first penetrated a soft surface layer – possibly a dust layer – several centimeters thick until they hit a hard surface – probably a sintered ice-dust layer – a few milliseconds later.”
Data from SESAME and other instruments indicate that activity in the form of vaporizing ice at Philae’s final landing site is low. Almost all the instruments in the lander did their jobs and returned data to mission control. Early results indicate that organic (carbon-based) molecules were detected, the drill performed as expected and at least went through the motions of delivering a soil sample to the probe’s oven for heating and analysis. What’s unclear is whether it gathered a sample in the first place.
Philae landed on a layer of dust about 4-8 inches (10-20 inches) deep. Beneath this relatively soft cover lies a bitter cold and firm crust of water ice. The MUPUS experiment hammered into the comet as hard as it could but was only able to penetrate a few millimeters. No wonder – the temperature just above the surface measures a nippy –243°F (–153°C). That’s some tough ice!
When the probe was lowered into the dust, the temperature dropped another 10 degrees Celsius.
With its batteries drained, Philae’s now in hibernation until at least next spring when the angle of the Sun on the comet will have changed to illuminate the solar panels. Assuming they begin producing electricity to recharge the batteries, there’s a chance we’ll be back in touch and downloading fresh information about the comet by summer.
Meanwhile, the Rosetta orbiter moves to the forefront:
“With lander delivery complete, Rosetta will resume routine science observations and we will transition to the ‘comet escort phase’,” said Flight Director Andrea Accomazzo.
Rosetta will have its “fingers” all over comet 67P/Churyumov-Gerasimenko during the upcoming mapping mission.
Rosetta is expected to stay with the comet at least through December 2015, so we can expect plenty of good science and (hopefully) a lot more close-up photos. On December 3, the craft will move down to a height of just 12.4 miles (20 km) above the surface for about 10 days, after which it will return to 18.6 miles (30 km). Team scientists want to get as close as possible to 67P/C-G before activity from jets of gas and dust becomes too risky to the spacecraft.
The upcoming low orbital volleys will be used to map the icy nucleus at high resolution and collect information on the comet’s gas, dust and plasma (molecules and atoms electrified by the Sun’s UV light).